A partnership has been formed between General Motors and the University of Wisconsin looking into high-speed petrol direct injection compression ignition operation in low temperature combustion of a light duty diesel engine.
It is hoped that the direct injection system could potentially reduce nitrogen oxides and PM from diesel engines.
Some of the findings made by researchers so far suggest that when using conventional petrol in a compression ignition engine, the larger ignition delay of petrol enables the engine to run at significantly higher loads with lower smoke and no detriment to fuel consumption. Others have found that the use of petrol in a diesel engine with a single injection strategy can reduce both nitrogen oxides and soot.
Now in their new study the researchers have concluded that gasoline direct injection compression ignition operation of light duty diesel engines is feasible and can extend low emissions engines. Thanks to the high volatility and low cetane index of petrol combined with the reduction of combustion temperature, both PM and nitrogen oxide emissions could be reduced at a level of about 0.1g/kg-f.
It also finds that there is an optimal injection pressure to maximise extension of the operation map for a given engine load condition and that operation maps are very sensitive to EGR ratio, initial gas temperature and boost pressure. Decreasing EGR ratio meanwhile, retards the injection timing range of the operation map.
